This invention concerns a hydraulic torque impulse generator of the type, comprising a motor driven drive member with a fluid chamber an output spindle connectable to a work piece and extending into the fluid chamber, two diametrically opposite seal elements movably supported in axial slots in the output spindle for sealing cooperation with seal lands on the fluid chamber wall, axially extending seal ribs on both of said fluid chamber wall and said output spindle, and a cam spindle drivingly coupled to the drive member and extending into a coaxial bore in the output spindle for engagement with the seal elements.
In previously known torque impulse generators of the above type, valve means have been incorporated to short circuit the impulse generating seal means every second time they coincide to avoid more than one torque impulse being generated for each relative revolution between the drive member and the output spindle.
In U.S. Pat. No. 4,884,995 there is shown a hydraulic torque impulse generator of the above type in which the cam spindle is provided with passage forming grooves which in cooperation with radial openings in the output spindle form short circuiting passages between the high and low pressure compartments of the fluid chamber.
One problem with this prior art impulse generator is that the valve means on the cam spindle and the output spindle create leakage points which require a very tight fit between the cam spindle and the output spindle to avoid reduced impulse magnitudes due to leakage. Extra passage forming means on the cam spindle and the output spindle as well as a very accurate fit between these elements cause increased manufacturing costs for the impulse generator.
The object of the invention is to solve the above-described problem.